Who is the RIAA, anyway?
The Recording Industry Association of America is a group that includes all of the major music recording companies, representing well over a thousand recording labels. In recent years they have strongly focused on preventing illegal distribution of music, and one result of this is lawsuits against people found to be illegally sharing copyrighted music through peer-to-peer software. You can see their website at http://www.riaa.com/. Note that a similar organization, the Motion Picture Association of America, fills the same role for the movie industry, and has been suing people who illegally share movies.